1. Field of the Invention
The present invention generally relates to the detection of hydrogen gas in a gaseous environment, and more specifically to an optical hydrogen gas detector apparatus and hydrogen gas detection method.
2. Background of the Invention
Hydrogen holds vast potential as a commercial source of energy. As reported by the Hydrogen Technology Advisory Panel, (HTAP), “[h]ydrogen will join electricity in the 21st Century as a primary energy carrier in the nation's sustainable energy future” (Vision Statement, The Green Hydrogen Report; The 1995 Progress Report of the Secretary of Energy's Hydrogen Technology Advisory Panel, DOE/GO-10095-179 May 1995). The abundance and versatility of hydrogen suggests that it can provide solutions to problems encountered with current fossil fuel energy systems, such as declining domestic supplies, air pollution, global warming, and national security.
Significant research and development efforts are currently underway to make the widespread use of hydrogen technically and economically feasible. These efforts are directed toward creating the basic infrastructure of a hydrogen economy: production, storage, transport and utilization. An underlying need of each of these infrastructural components is the ability to detect and quantify the amount of hydrogen gas present in a gaseous environment. This is critical not only for health and for human safety reasons, but will be required as a means of monitoring hydrogen-based technology and for the development of high-efficiency hydrogen processes. Hydrogen gas sensors that can quickly and reliably detect hydrogen over a wide range of oxygen and moisture concentrations are not currently available, and must be developed in order to facilitate the transition to a hydrogen-based energy economy.
Hydrogen is the lightest and most abundant element in the universe. As a gas, hydrogen is odorless, colorless, and burns with a virtually invisible flame (an effective odorant and luminant with minimal system and emission impact has not yet been developed). It has a lower explosive limit (LEL) of 4% in air, and an upper explosive limit (UEL) of 75%. The minimum self-ignition temperature of a stoichiometric mixture of hydrogen and oxygen is 585° C.
Although the safety record of the commercial hydrogen industry has been excellent, it is estimated that undetected leaks were involved in 40% of industrial hydrogen incidents that did occur (“The Sourcebook for Hydrogen Applications,” by the Hydrogen Research Institute and the National Renewable Energy Laboratory, 1998). Emerging hydrogen-based energy systems will require hydrogen sensors that are as ubiquitous as computer chips have become in current home, office, factory and vehicular environments. This circumstance in turn requires that massive numbers of hydrogen sensors be readily manufacturable at low cost.
In this respect, any commercially viable hydrogen detector must satisfy the following requirements:    the detector must be selective to hydrogen in a wide variety of gaseous environments, including oxygen-rich, high-humidity environments found in fuel cells;    the detector must have a good signal-to-noise ratio and a large dynamic range;    the detector should minimize both failures to detect and false positives;    the detector must operate rapidly, inasmuch as high speed detection is a critical requirement to ensure rapid response to potentially hazardous leaks of hydrogen;    the detector must have a long lifetime between calibrations, in order to minimize maintenance requirements and achieve low lifetime costs with high reliability;    the detector must be characterized by low power consumption, which is particularly critical for portable instrumentation and personnel monitoring device applications;    the hydrogen detector should be characterized by a high level of operational safety, and should not depend on any heated wire, open flame, or spark for its operation; and    the hydrogen detector must be reliably and reproducibly manufacturable at high volumes, and be readily available in great numbers, at low cost, to achieve ubiquitous monitoring of numerous, dynamically changing and diverse environments.